全新java初学者实践教程6(Java SE5.0版)
W6 H,6v 基本语法3
+5VLw z4M9M7)" 4lhw3,5 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
,1OyN]f3 FIxFnh3~ [font="Times] 1.循环语句[font="Times]:while,do-while,for
=0uAE7q(9 26T "XW'_ [font="Times]2.分支语句[font="Times]:if-else,switch,
MUfG?r\t [font="Times]
bwiPS1+); 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
4vBL6!z:Z [font="Times]
0cK{ 4.异常处理语句[font="Times]:try-catch-finally,throw
U!U$x74D5 7$h#OV*@, 实践:
L_=3<nE [font="Times] 1.循环语句
[q !TIq [font="Times] while 语句
rV08ad [font="Times]class While {
K2%w0ohC [font="Times]public static void main(String args[]) {
p+)Y Tzzc [font="Times]int n = 10;
a7N!B' y [font="Times]while(n > 0) {
e[hcJz!D [font="Times]System.out.println("tick " + n);
Xy5e5K [font="Times]n--;
V5*OA??k< [font="Times]}
4Y[1aQ(% [font="Times]}
6k#Jpmmr [font="Times]}
M Y|w [font="Times] do…while 语句
x c{hC4^V [font="Times] class DoWhile {
[l,Ei? [font="Times]public static void main(String args[]) {
g<~Cpd [font="Times]int n = 10;
M)SEn/T- [font="Times]do {
2RSt)3!}, [font="Times]System.out.println("tick " + n);
_a1x\,R|DB [font="Times]n--;
lok= [font="Times]} while(n > 0);
S~|T4q( [font="Times]}
qvPtyc^fN [font="Times]}
8<Hf"M 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
fkac_X$7 [font="Times] for语句
KZ/=IP= [font="Times] class ForTick {
=ZqT3_ [font="Times]public static void main(String args[]) {
H)n9O/u [font="Times]int n;
F i0GknQ+ [font="Times]for(n=10; n>0; n--)
Hw4%uS==V [font="Times]System.out.println("tick " + n);
RsYU59_Y [font="Times]}
Hro-d1J7 [font="Times]}
WYr/oRO 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
>3Eo@J,?d 还有啊,[font="Times]for循环的部分可以为空的
<~WsD)=$ [font="Times]class ForVar {
@ta7"6p-i@ [font="Times]public static void main(String args[]) {
OLE[UXD-E [font="Times]int i;
P?k0zwOlBl [font="Times]boolean done = false;
:5{wf Am [font="Times]i = 0;
>6?__v]9G [font="Times]for( ; !done; ) {
_ jsK}- \ [font="Times]System.out.println("i is " + i);
"yS _s [font="Times]if(i == 10) done = true;
sfNE68I2 [font="Times]i++;
3U0`,c\ao* [font="Times]}
}|pwz [font="Times]}
9?SZNL['V [font="Times]}
循环语句的例子下载 OOo3G~2r [font="Times] 2.分支语句[font="Times]
X<I+&Zi [font="Times] if/else语句
bJX)$G [font="Times]class IfElse {
<P=twT;P [font="Times]public static void main(String args[]) {
o6uJyCO [font="Times]int month = 4; // April
p"KFJ [font="Times]String season;
o{y9r{~A [font="Times]if(month == 12 || month == 1 || month == 2)
]jo1{IcI [font="Times]season = "Winter";
C@'h<[v`1v [font="Times]else if(month == 3 || month == 4 || month == 5)
?k(7 LX0j [font="Times]season = "Spring";
tg<EY!WY [font="Times]else if(month == 6 || month == 7 || month == 8)
*=V~YF:Qb [font="Times]season = "Summer";
UdpF@Q [font="Times]else if(month == 9 || month == 10 || month == 11)
T9Nb`sbV] [font="Times]season = "Autumn";
75XJL;W # [font="Times]else
?B2] -+Y [font="Times]season = "Bogus Month";
&B6Ep6QS [font="Times]System.out.println("April is in the " + season + ".");
Hl{S]]z [font="Times]}
8@MV%MVy$ [font="Times]}
}&wUr>= [font="Times]//这段程序输出[font="Times]:
JzQ )jdvp [font="Times]//April is in the Spring.
SAy=WV [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
VHIOwzC [font="Times] switch语句
JvVWG'Z" [font="Times] class Switch {
nU7>uU [font="Times]public static void main(String args[]) {
Brf5dT49 [font="Times]int month = 4;
ahJ`$U4n [font="Times]String season;
3=aQG'B [font="Times]switch (month) {
Nn!+,;ut [font="Times]case 12:
%C|n9* [font="Times]case 1:
~?d Nd [font="Times]case 2:
y1dDO2mA [font="Times]season = "Winter";
,$s8GAmq [font="Times]break;
M
l Jo`d [font="Times]case 3:
/|C* [font="Times]case 4:
1g8_Xe4 [font="Times]case 5:
F8jd'OR [font="Times]season = "Spring";
K,+LG7ec [font="Times]break;
PQ5QA61 [font="Times]case 6:
C~2F9Pg [font="Times]case 7:
QdF5Cwf4 [font="Times]case 8:
6-$jkto [font="Times]season = "Summer";
p<2L.\6" [font="Times]break;
E8$20Ue [font="Times]case 9:
7%Gwc?[x [font="Times]case 10:
zzTfYf) [font="Times]case 11:
B+\3-q [font="Times]season = "Autumn";
s4A43i'g!h [font="Times]break;
BJ$9vbhZN [font="Times]default:
f$e[u
Er [font="Times]season = "Bogus Month";
[ 9 {*94M [font="Times]}
Wbr|_W [font="Times]System.out.println("April is in the " + season + ".");
&"f"; [font="Times]}
]zE;Tw.S [font="Times]}
分支语句代码下载 _aGOb;h Ugu[|, [font="Times]switch语句适合于条件非常多的逻辑
v1o#1; 请看上述语句可以混合使用,请看
下载例子